1. Field of the Invention
The present invention relates to an improved liquid crystal display (LCD) device and an improved method of forming the array of conductors in an LCD device and, more particularly, to an improved thin film transistor active matrix LCD device and an improved method of forming the thin film transistor active matrix LCD device, the improvement coming from being able to prevent conductors in the array from becoming cut by internal stresses in the conductors caused by step coverage.
2. Description of Related Art
Generally, an active matrix for use in an LCD device includes a thin film transistor (TFT) connected to each pixel via a pixel electrode. The TFT is connected to a gating circuit through a metal gate line and to a metal signal (or data) line for transmitting a signal from a driving circuit to a pixel electrode made of indium tin oxide (ITO).
As shown in FIG. 1, an active matrix of a liquid crystal display device includes a gate electrode 1 of a thin film transistor, which is connected to a gate line 5, a drain electrode 2 connected to a signal (or data) line 4, and a source electrode 3 connected to a pixel electrode 6. In such an active matrix, if the gate line is enabled(i.e., an increased voltage is applied on the gate line 5), then the TFT turns on and a picture signal, if any, inputted by the signal line 4 is transmitted to the pixel electrode 6. By selectively applying signals to all the pixels in an LCD, a desired picture appears on the liquid crystal display.
FIGS. 2 and 3 illustrate cross-sections of FIG. 1. The LCD uses the ITO on passivation (IOP) technique to form the pixel 6. The transparent ITO pixel 6 is prepared by the following method. First of all, after a metal such as Cr, Ta, Al, etc., is deposited on a substrate 10 by a sputtering method, it is patterned by a photoreading method and gate electrode 1 and gate line 5 are formed on the substrate. Thereafter, an insulating layer 9 such as SiNx, SiO.sub.2, etc., is deposited on the substrate 10 having the gate electrode 1 and the gate line 5 formed thereon. Then, a semiconductor layer 7 is deposited thereon by the plasma CVD (chemical vapor deposition) method, and subsequently patterned.
Subsequently, a metal composed of Al or Al alloy is deposited by sputtering and then is patterned to form the signal (or data) line 4, the drain electrode 2 and the source electrode 3. Then a protective layer 8 is deposited thereon. After a contacting hole 11 is formed in the protective layer 8 (located at the end of the source electrode 3) by patterning, the pixel electrode 6 is formed on a pixel region of the substrate 10 and also is formed in the contacting hole region so that the pixel electrode 6 connects to the source electrode 3.
However, such a conventional active matrix for a liquid crystal display device as shown in FIGS. 1, 2 and 3, suffers from a number of problems. For example, the signal(or data) line or the source and drain lines frequently are cut because the overlying lines, being made of metal, are susceptible to the weaknesses of conforming to a stepped shape. That is, the signal or data line 4 can become cut due to having to conform, i.e., cross the stepped shape of the gate line 5 at the portion B where the gate line 5 crosses under the signal line 4. Alternatively, the source and drain electrodes 2 and 3 can become cut at the portion A (FIG. 1) of TFT due to the weaknesses imposed by the step coverage.